motor root

Examples of motor root in the following topics:

• Parasympathetic (Craniosacral) Division

  • Each has three roots entering the ganglion (motor, sympathetic, and sensory roots) and a variable number of exiting branches.
  • The motor root carries presynaptic parasympathetic nerve fibers (general visceral efferent fibers) that terminate in the ganglion by creating a synapse for the postsynaptic fibers traveling to target organs.
  • The sympathetic root carries postsynaptic sympathetic fibers (general visceral efferent fibers) that traverse the ganglion without creating a synapse.
  • The sensory root carries general sensory fibers (general somatic afferent fibers) that also do not create a synapse in the ganglion.

• Trigeminal (V) Nerve

  • The trigeminal nerve (cranial nerve V), and it contains both sensory and motor fibers.
  • The motor function activates the muscles of the jaw, mouth, and inner ear.
  • The mandibular nerve has both sensory and motor functions.
  • From the trigeminal ganglion, a single large sensory root enters the brainstem at the level of the pons.
  • Immediately adjacent to the sensory root, a smaller motor root emerges from the pons at the same level.

• Overview of the Spinal Cord

  • Thirty-one pairs of spinal nerves (sensory and motor) branch from the human spinal cord.
  • The posterior root is the sensory (afferent) root that carries sensory information to the brain from other areas of the body.
  • The anterior root is the motor (efferent) root that carries motor information to the body from the brain.
  • The swelling found in the posterior root is the posterior (dorsal) root ganglion, which contains the cell bodies of sensory neurons.
  • The anterior (ventral) root contains axons of motor neurons that conduct nerve impulses from the CNS to other parts of the body such as the muscles.

• Sensory-Somatic Nervous System

  • Other cranial nerves transmit almost solely motor information.
  • The sensory neuron cell bodies are grouped in structures called dorsal root ganglia .
  • Motor neurons have cell bodies in the ventral gray matter of the spinal cord that project to muscle through the ventral root.
  • Spinal nerves contain both sensory and motor axons.
  • The cell bodies of sensory neurons are located in dorsal root ganglia.

• Spinal Cord Grey Matter and Spinal Roots

  • The grey matter, in the center of the cord, is shaped like a butterfly and consists of cell bodies of interneurons and motor neurons, as well as neuroglia cells and unmyelinated axons.
  • The axons of dorsal root ganglion neurons are known as afferents.
  • Ventral roots consist of axons from motor neurons, which bring information to the periphery from cell bodies within the CNS.
  • Dorsal roots and ventral roots come together and exit the intervertebral foramina as they become spinal nerves.
  • Describe the grey matter and spinal roots of the spinal cord

• Overview of the Spinal Nerves

  • Each spinal nerve is formed by the combination of nerve fibers from the dorsal and ventral roots of the spinal cord.
  • The dorsal roots carry afferent sensory axons, while the ventral roots carry efferent motor axons.
  • The dorsal ramus contains nerves that serve the dorsal portions of the trunk; it carries visceral motor, somatic motor, and somatic sensory information to and from the skin and muscles of the back (epaxial muscles).
  • Its anterior root helps form the coccygeal plexus.
  • Spinal nerves arise from a combination of nerve fibers from the dorsal and ventral roots of the spinal cord.

• Motor Units

  • The motor unit is the functional unit of muscle contraction and includes the motor nerve fiber and the muscle fibers it innervates.
  • A motor unit consists of the motor neuron and the grouping of muscle fibers innervated by the neuron.
  • Thus, small motor units can exercise greater precision of movement compared to larger motor units.
  • Groups of motor units are innervated to coordinate contraction of a whole muscle and generate appropriate movement; all of the motor units within a muscle are considered a motor pool.
  • These multiple motor units of different sizes within a motor pool allow for very fine control of force either spatially or temporally.

• Sensory and Motor Tracts

  • The spinothalamic tract is a somatosensory tract and the corticospinal tract is a motor tract.
  • In both pathways, primary sensory neuron cell bodies are found in the dorsal root ganglia, and their central axons project into the spinal cord.
  • It contains mostly motor axons.
  • The primary purpose of the corticospinal tract is to maintain voluntary motor control of the body and limbs.

• Spinal Cord Trauma

  • SCI can have a number of causes; examples include motor vehicle accidents, falls, sports injuries, and violence.
  • Depending on where the spinal cord and nerve roots are damaged, the symptoms can vary widely, from pain to paralysis to incontinence.
  • A indicates a "complete" spinal cord injury where no motor or sensory function is preserved in the sacral segments S4-S5.
  • This is typically a transient phase and if the person recovers any motor function below the neurological level, that person essentially becomes a motor incomplete, i.e.
  • E indicates "normal" where motor and sensory scores are normal.

• Motor Areas

  • The motor areas of the brain are located in both hemispheres of the cortex.
  • The right half of the motor area controls the left side of the body, and the left half of the motor area controls the right side of the body.
  • Premotor cortex: Located anterior to the primary motor cortex and responsible for some aspects of motor control.
  • Various experiments examining the motor cortex map showed that each point in motor cortex influences a range of muscles and joints, indicating significant overlapping in the map.
  • $$Topography of the human motor cortex, including the premotor cortex, SMA, primary motor cortex, primary somatosensory cortex, and posterior parietal cortex.